Fuel cutoff switch?

[arch252]

I just picked up a Troy Bilt Bronco with a twin cylinder 18.5hp ELS500 engine. Sorry, I don't think I'm going to be able to find the engine code without taking the hood and side panels off.

The guy I bought it from said he had taken it to a local service center, one that I know to be reputable, for a fuel issue. He showed me where they installed a fuel cutoff valve between the tank and engine. He said you have to keep the valvle closed when it is not running or fuel will run into the crankcase. He said they told them is was some kind of valve issue.

Can someone please tell me what problem they were attempting to correct so that I can try to fix it properly? Would it have something to do with the fuel pump? I would think it would have to be something fairly costly in parts or labor for them to just install a cutoff switch rather than fix the problem. Any help would be appreciated.

 

[mechanic mark]

"K&T Parts House Lawn Mower Parts and Chain Saw & Trimmer Parts" You may very well have a carburetor problem, post numbers when you have time as well as engine manufacturer, thanks. Example B&S engine: model xxxxxx, type xxxx, trim xx.

 

[deamer1]

Many two cyl. Mower engines have a fuel cutoff solenoid located at the fuel input to the carburetor. When the ignition key is off, the 12 volt from the battery is cut off to the solenoid and no gas flows into the fuel bowl. When the key is in the crank or run position, the 12 volts is applied to the fuel solenoid and fuel will flow into the carburetors fuel bowl. It prevents engine run on after turning off the key. There are other factors which eliminate the engine to continue running, but I won't cover that at this time.

I have experienced bad solenoids in the past. Testing them is fairly easy and quick. The price of a new solenoid may shock you. An example of a new fuel solenoid on my Scag Turf Tiger is approximately $135.00 retail. The Carburetor is $400.00 Plus.

Your description indicates a attempt to get the mower up and running in a inexpensive manner. :confused2:

Suggest you provide your engine and mower models and serial numbers...You'll get more input from knowledgeable people when it's provided. :thumbsup:

Good luck on your project.


Deamer1

 

[arch252]

All very good info, thanks! My first thought was a carb issue, I was thinking maybe a bad float or something like that. When he said they told him it was a valve issue I didn't really know what to make of that. I have worked on a JD mower that had the electrical solenoid on the bottom of the carb. When I first ran across one it took a moment to figure out what I was dealing with. I thought I had a bad solenoid on that mower but I had an identical mower and engine and swapped the solenoid and ruled out that problem, that ended up being an issue with the fuel pump. I do remember pricing the solenoid on that engine and yes, I was suprised at how expensive it was. This certainly seems like a very likely candidate for the problem with this mower.

I will do my best to provide the engine numbers tomorrow and I may pull that solenoid off and test it. I picked up this great looking Bronco for $150. I needs a minor deck repair that I should be able to manage with a little welding. Other than that it looks great and runs great. I think it would be worth it to spend the money on the solenoid if that is the problem to make it right. Using the fuel cutoff switch just isn't going to get it.

 

[Rivets]

The valve the guy was talking about is the float needle valve, not the fuel shutoff solenoid. What you need to do is remove the carb and give it a 24 bath and cleaning. Then replace the float needle and seat before reassembling. Should solve the problem he tried to fix with a bandaid (installing an inline shutoff valve).

 

[arch252]

Yes, that could be, I didn't think of it that way. Apparently they didn't explain it well to the guy I got it from either. He thought they were talking about the intake/exhaust valves. I asked him if it could be an issue with the carb and he said, "No, not the carb, they told me it was the valves." At any rate, that could very well be the issue. I just find that hard to believe, that a reputable service center would not pull the carb and clean it, that's easy stuff, not time consuming at all and the carb rebuild kit is just a few bucks. The guy I got it from ended up buying a $1,400 Husqvarna, had it sitting in his garage, so I doubt he would have told them not to clean it for a few $$ more. I don't know what a pro charges for a carb rebuild but really it's about an hour in labor and $20 in parts. I'm sure they didn't do the fuel cutoff for free, even though they should have, so how much could he have saved?

So if I drop the bowl and lift the float and gas is still running out I'm guessing I've found the problem, correct? If not then I guess I'll continue on to check the solenoid.

 

[Rivets]

If you just drop the bowl, push up the float, and the fuel stops, it does not mean that the needle and seat are good. The needle should seat with 7 pounds of pressure, that's not much, as you can put 10 pounds on with no effort. I recommend clean carb and replace, based on your symptoms. Why it was not done by a reputable firm is puzzling, as depending on the unit it takes 30-45 minutes and the kit costs $5-25. 90% of the people on this forum say go the cheap way, but as I said, it is a bandaid. Here is the procedure we use in our shop and it works 96% of the time, the other 5% the carb needs to be replaced. Not all the carbs are the same, so you may have to tweak it for your situation.

Needle and seat replacement

Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.

I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.

With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. *Next check to make sure that the float does not have any liquid in it. *If it does, replace. *If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.

PS: *On the side of some Tecumseh carbs you will find a plastic cover. *Under this cover will be an idle jet. *Remove it and check to see that the jet is open both horizontally and vertically. *You should be able to push the old float needle wire through the vertical opening.

 

[SeniorCitizen]

The float must actually float for the needle valve to be effective.

 

[arch252]

Okay, so thank you Briggs for putting the engine code on the back side one inch away from the gas tank. With the help of a small mirror I got the engine code, 5B5SX 5012VP, Model 276016.

I went ahead and took the carb off. I've done quite a few carbs now and I follow the same procedure that Senior described. Most of my experience is with older Briggs, Tecumseh, and Robin. These newer Briggs engines are still new to me. The carb was pretty standard and it did have the solenoid. I skipped testing the solenoid because I figured even if the solenoid was bad it shouldn't matter, the fuel shouldn't be getting past the inlet valve if the float is working properly.

I removed the plastic float, it was in good condition. I removed the needle, it was the larger needle with a black tip. There was no red rubber seat in the inlet, no rubber seat at all, just the metal inlet hole. I've seen this on one other carb I've worked on and I dug in there forever and then searched for hours certain that I had just dropped it. I'm guessing there are no rubber seats needed with these black tipped needles. Someone tell me if this is wrong. Trust me though, there is no rubber seat in this one, just metal. If one does belong in there I can't image where it went, unless Ethanol fuel completely dissolved it.

I cleaned it thoroughly and put it back on. It was too late tonight to test anything out. I attached a photo, I left the intake manifold loose where I am pointing in the picture and I turned the fuel cutoff switch on to let the fuel flow. Nothing came out of the loose manifold opening. I'm guessing that if fuel was still running past the float and inlet needle valve it would be running out of that manifold opening, correct? I left it open for a few minutes and then closed the cutoff valve and left it for tonight. Is there a better way to know if the problem is fixed?

If the problem is fixed then I figure I should probably change the oil in case any fuel has run into the crankcase.

I'm wondering how a problem like this would be first discovered. Does the fuel running into the crankcase cause the engine to smoke or run rough? What are the signs in case it happens again. I'm guessing having fuel in the crankcase would be a quick way to seize an engine.

 

[SeniorCitizen]

I don't recall ever seeing a seat with rubber ( neoprene). The evolution of needles changed from metal only to neoprene tips probably over 50 years ago. I've read that a correctly working solenoid valve on the carburetor doesn't prevent the flow of gas into the crankcase. I've personally never investigated that but just took the author's word.